BestForPets is reader-supported. Your purchases via our links may earn us an affiliate commission at no extra cost to you. Our Affiliate Disclaimer

9 Mistakes To Avoid Making As A Goldfish Keeper

We all want to be the greatest possible goldfish caretakers for our aquatic companions, and we all care much about our goldfish and giving them the happiest, healthiest life possible.

While some individuals actively seek to be ignorant about good goldfish husbandry, the vast majority of individuals really care and accidentally commit errors that are highly prevalent among novice and unskilled goldfish keepers.

There is no need to berate yourself if you are dealing with a sick fish or attempting to correct a mistake you made.

Continue reading "9 Mistakes to Avoid Making as a Goldfish Keeper" by BestForPets (bestforpets.org), which demonstrates that you want to provide the best care for your goldfish.

Give Yourself a Break!

We all make errors. Not only do we all make errors, but we must all begin someplace, albeit not everyone begins in the same location. If your buddy did not make the same mistakes as you,

it does not indicate that one of you is a superior goldfish keeper. It simply indicates that you and your opponent have distinct beginning places and different levels of fundamental knowledge.

Mistakes you may have avoided making may very well be the ones your buddy is currently experiencing. The finest thing we can do for our goldfish is to support and encourage one another, offering gentle correction and safe knowledge to help us all become the best goldfish caretakers we are capable of becoming.

Continue reading to learn how to prevent some of the most frequent mistakes made by goldfish caretakers.

9 Common Goldfish Keeping Mistakes:

1. Not Cycling the Tank

This is by far the most frequent error individuals make while maintaining goldfish or any other species of fish. Most individuals are accustomed to going to the shop, purchasing a bowl or tank and fish, and bringing everything home to get started. According to scientific knowledge, this is incompatible with appropriate tank cycling.

Tank cycling is the process of developing colonies of beneficial microorganisms within the aquarium. These colonies inhabit the filter, substrate, and various other surfaces where water flows throughout the aquarium.

Beneficial bacteria eat fish waste products ammonia and nitrite and convert them to nitrate. Nitrate is the last result of the nitrogen cycle and the primary reason we change the water in a fish tank (more on that later). In addition to reducing nitrate levels in the aquarium, plants use nitrate as a fertilizer.

It is possible to do a fish-in cycle, which involves cycling the aquarium with the fish already present. However, this is not an ideal situation. Allowing ammonia levels to rise so that beneficial bacteria have something to eat for energy, development, and reproduction is the most important aspect of cycling a tank.

Both ammonia and nitrite can cause temporary or permanent harm to fish, and the optimal ammonia and nitrite levels for a fish tank are zero.

As you may guess, this makes it challenging to execute a fish-in cycle securely. There are solutions on the market that include helpful bacteria in a bottle, which can expedite the tank cycling process. However, these items are not a suitable substitute for tank cycling.

Depending on a number of variables, cycling your aquarium with or without fish might take anywhere from a few days to many months. It is a process that requires time and care, especially if the tank contains fish.

2. Not Researching the Needs of Goldfish

If you had fish as a child, you undoubtedly remember standing in the aisles of a pet store, selecting tank decorations, purchasing fish food and a heater, and then taking your new goldfish home to settle in. Many individuals are unaware of the special demands of goldfish.

The most common error made by individuals is keeping goldfish in heated tanks or bowls. Goldfish are cool-water fish, so if their surroundings is climate-controlled, such as your living room with air conditioning and heating, they will likely not need a heater. This is true of the majority of households, although it is not always the case.

On the surface, keeping your goldfish in warm water does not appear to be an issue. What you may not notice until it is too late is the harmful effect it is having on your goldfish.

Keeping goldfish in warm-water habitats can reduce their lifespan by years or even decades. Providing a suitable tank temperature for your goldfish is essential for guaranteeing their longevity.

Additionally, you may not understand that some goldfish, especially fancy varieties, do not perform well in environments with sharp or jagged edges. These abrasive surfaces can snag and rip sensitive fins, exposing them to infection and stress.

The substrate that you pick for your goldfish is another factor to consider while setting up your aquarium. Most individuals simply grab a bag of gravel and call it a day, but goldfish have been observed with gravel in their mouths. This may necessitate human intervention and may result in the fish’s harm or death.

Goldfish are often safer in fine substrates, such as sand, or in bigger substrates, such as large pebbles or river rocks, since they are less likely to become entangled. Some individuals opt not to provide a substrate for their goldfish.

3. Choosing Inappropriate Tank Mates

Many individuals employ the “go to the store, pick out fish” strategy when selecting fish. In the end, individuals chose fish primarily on beauty and disregard the special requirements of each species.

Therefore, if you purchase goldfish and tropical freshwater fish, such as angelfish, one of the species will not be able to survive in less-than-ideal water conditions, as goldfish need chilly water while angelfish prefer warm water.

Some individuals purchase betta fish and goldfish without comprehending the stress and risk this poses for both species, which frequently results in violence and death. Another frequent error made with goldfish is selecting tiny tankmates.

There is some overlap in the environmental preferences of goldfish and guppies, however goldfish will consume nearly anything that can fit in their mouths. This contains both fry and adult guppies.

Some individuals assert that goldfish cannot be housed in a tank alongside other fish due to their messiness. This is not true, thankfully. Suitable tankmates for goldfish include giant snails, such as mystery snails, and other cool-water fish, such as dojo loaches.

However, caution should be used while selecting goldfish tankmates. Choosing unsuitable tankmates will certainly result in grief for you and stress for the surviving fish.

4. Overstocking the Tank

We’ve been informed for a very long time that there are “rules” about the size of the tank a goldfish should be kept in. There are size concerns, but there are no hard and fast restrictions.

Many individuals believe that goldfish will not outgrow their habitat because goldfish create hormones that inhibit development and are discharged into the water. This is partially accurate, but not totally so.

If you purchase eight 2-inch goldfish for a 10-gallon tank, you have overstocked the tank, despite the fact that they are still little. Even if their growth is stunted, they may get uncomfortable or feel the urge to compete for resources.

An overstocked aquarium may be maintained safely and healthily. Maintaining water quality and health only demands greater preparation and commitment to regular tank maintenance.

There is, however, such a thing as an overstocked tank, so ensure that your goldfish and other tank inhabitants have adequate room to feel secure and happy and that they all have equal access to resources, such as food.

5. Under-filtering the Tank

Goldfish are incredibly efficient producers of bioload! A single adult goldfish generates more trash than ten ember tetras. Numerous individuals make an error while selecting aquarium filtration, and it is easy to comprehend why.

If you have a 55-gallon tank and find a filter rated for a 50-gallon tank, you may conclude that it will suffice. Regarding low bioload producers, you are likely correct.

Regarding goldfish, you are undoubtedly incorrect. If there are one or two goldfish in a tank, then the filter should be rated for the size of the tank. If your aquarium is overstocked, you will need a filter suited for a larger aquarium than your own.

A strong filter, such as a HOB or canister filter, and a filter that allows more area for beneficial bacteria, such as a sponge filter, are both recommended for goldfish. You will almost probably not over-filter your aquarium, but it is possible to under-filter it!

In addition to removing visible and microscopic debris, proper filtration also colonizes beneficial bacteria and aerates the tank water. Do not, under any circumstances, underfilter your aquarium. You will be sorry!

6. Poor Dietary Decisions

Similar to all other animals, goldfish require a properly balanced diet. Commercial goldfish food is the ideal foundation for your goldfish’s diet since it is intended to match their nutritional requirements. These meals give neither diversity nor balance.

In addition, they supply the minimal minimum of nutrients, but not necessarily satisfaction. In the wild, goldfish and Prussian carp consume aquatic vegetation and tiny creatures, such as freshwater shrimp, throughout the day.

As you might expect, feeding your goldfish fish meal pellets twice a day does not satisfy them in the same way that grazing would.

Your goldfish’s primary food source should ideally be pellets. In comparison to pellets, flakes often include more fillers and less nutrients. Gel foods, freeze-dried foods, frozen foods, and live foods should also be included in your goldfish’s diet on a regular basis.

Your goldfish should have access to fresh vegetables and fruits at all times. The finest selections are leafy green vegetables, such as romaine lettuce, spinach, arugula, and herbs; nevertheless, they may also consume zucchini, butternut squash, cucumber, broccoli, brussels sprouts, bananas, strawberries, and apples.

To prevent digestion and swim bladder issues, high sugar meals, such as fruits, and high protein foods, such as bloodworms, should be provided sparingly and only as a treat.

7. Improper Tank Maintenance

Once your tank has been cycled and your goldfish have been acclimated, you may believe it is OK to perform water changes every few months or perhaps once a year.

Do you recall the nitrogen cycle? Nitrates will accumulate in your aquarium, and standard filter media will not be able to remove them. Up to 20 ppm of nitrates are typically regarded acceptable in a cycled aquarium, while some individuals believe that up to 40 ppm is safe.

If you’re not conducting water changes and you don’t have a hundred plants in your aquarium, nitrates are probably not leaving your tank. This means that they will continue to accumulate, to the detriment of the residents in your tank. Routine water changes will assist in eliminating these extra nitrates.

Another issue with nitrates in excess in your aquarium? Algae! Algae are plants, thus they collect nitrates from the water in order to thrive. In a well-balanced aquarium, plants absorb the majority of nitrates while water changes remove the remainder. However, if you do not remove extra nitrates, algae might establish a stronghold in your aquarium by absorbing the nitrates that your plants are not utilizing.

Algae is not only unattractive. It can reach a size where it outcompetes other plants, suffocating them by eating all the nutrients.

8. Treatment vs Prevention:

Do you wish to learn a not-so-secret secret? The leading cause of sickness in goldfish is poor water quality!

People frequently make the mistake of treating their goldfish with medication when they observe them displaying signs of disease. However, treating disease will be ineffective if the water parameters are incorrect and the water quality is inadequate.

In actuality, you are only contributing to an already stressful setting. Some sick goldfish may not even survive medicine therapy, so exposing them to this extra stress during a period of sickness that can be addressed with a simple water change or water treatment might be more detrimental than beneficial.

Additionally, it is crucial to remember that drug-resistant microorganisms exist. You increase the chance for antibiotic resistance if you give your goldfish antibiotics that they do not require or if you do not finish a course of therapy after beginning it.

Infections that are resistant to antibiotics are exceedingly difficult to cure, and even if your fish dies, you may struggle to remove the infectious organism from the aquarium. The most effective therapy for disease in goldfish is prevention, not treatment.

Proper aquarium maintenance, including periodic water changes, water treatment, and parameter monitoring, is superior than any medicine.

9. Changing the Filter Media

If you study the filter’s instructions, you will likely discover that the manufacturer suggests replacing filter media or cartridges every few weeks. Usually, diligent goldfish caretakers adhere to this, unwittingly disrupting the tank’s cycle each time.

Remember that helpful bacteria reside in the filter and filter media of the aquarium. This implies that each time you replace the filter cartridge, a substantial amount of your beneficial bacteria are eliminated.

Honestly, you should seldom update your filter media. When doing water changes, it is recommended to rinse the new water in filthy tank water to remove “gunk” without killing beneficial bacteria. By rinsing your filter media with hot water in the kitchen sink, you eliminate the helpful bacteria.

The majority of knowledgeable goldfish keepers advise replacing the filter cartridges with long-lasting filter sponges and ceramic rings or beads that may be rinsed occasionally without replacement. This will help you maximize your investment and prevent you from destroying your cycle every few weeks.


As a goldfish keeper, errors are exceedingly easy to commit. Proper husbandry requires a great deal of knowledge and experience, which can be time-consuming. Do not punish yourself if you find you have been making errors. Accept the lesson, resolve the issue, and proceed.

9 Mistakes to Avoid Making as a Goldfish Keeper” by BestForPets (bestforpets.org) hopefully helps you understand more about your goldfish and how to keep them healthy.

Author Image

Dr. Deborah Fletcher

Deborah R. Fletcher, DVM, is a skilled veterinarian with more than 15 years of experience dealing with companion and exotic animals. She has experience caring for a variety of animals, including household cats and dogs, reptiles, birds of prey, and even primates. Dr. Fletcher is a valuable part of the BestForPets team, where she contributes to their aim of providing pets and their owners with the finest possible treatment and services.

Veterinarian (DVM) Dr. Deborah Fletcher


Rated 0 out of 5
0 out of 5 stars (based on 0 reviews)
Very good0%

There are no reviews yet. Be the first one to write one.

Related articles